Energy absorbing rotary piston pump

ABSTRACT

An energy absorbing device, which is highly effective for use in an aircraft arresting gear, is provided by mounting a rotary pump having a pressure related characteristic within a container of fluid. The pump circulates the fluid from and back into the container whereby it absorbs energy in response to a mechanical input and transmits this energy to the fluid in the container in the form of heat. A highly effective form of this device utilizes a rotary piston-type pump having an axial input channel in its shaft connected to radial passageways extending through its cam disc and rotating piston. The fluid is discharged through pressure relief valves of the compressed air cushioned type. The rotary piston-type pump is particularly advantageous for such service because its rotor rotates slower than the input shaft, thus minimizing the mass of the pump to provide a given amount of energy absorption.

1 e lilssste gtates Patent 1151 3,6553% Qotton 54 ENERGY SQHNG ROTYPISTON 3,452,723 7/1969 Keylwert ..l23/8.07 PUMP FOREIGN PATENTS ORAPPLICATIONS [72] Inventor: Robert 13. Cotton, Media, Pa. 1,133,76211/1956 France [73] Assignee: All American Industries, linc.,Wilmington,

Del. Primary Examiner-Carlton R. Croyle Assistant Examiner-John J.Vrablik [22] Wed: 1970 AttorneyConnolly and Hutz [21] Appl. N0.: 84,825

[57] ABSTRACT Related Application Dam An energy absorbing device, whichis highly effective for use [63] Continuation-impart of Ser. No.756,035, Aug. 28, in an aircraft arresting gear, is provided by mountinga rotary 1968, Pat. No. 3,549,110.

pump having a pressure related characteristic within a container offluid. The pump circulates the fluid from and back [52] U.S. Cl..4l8/61, 418/188 into the n in r her by it absorbs energy in responseto a [51] Int. Cl ..F0lc1/02, F04c 1/02, F040 15/02 mechanical input n rn mi his energy to the fl id in the 53 Field of Search ..418/60, 61,183, 185, 186-188; container in the form of heat A highly effective formof this 123/833 3 5 device utilizes a rotary piston-type pump having anaxial input channel in its shaft connected to radial passagewaysextending 56 R f C-ted throu h its cam disc and rotating piston. Thefluid is I 1 e Memes disch rged through pressure relief valves of thecompressed UNITED STATES PATENTS air cushioned type. The rotarypiston-type pump is particularly advantageous for such service becauseits rotor rotates 3,l 15,871 12/1963 LllClf ..418/61 slower than the i pshaft, thus the mass of the 3,255,737 6/1966 Nallinger ..418/61 pump toprovide a given amount ofenergy absorption. 3,340,853 9/1967 Link..418/61 3,413,961 12/1968 Keylwert ..123/8.45 5 Claims, 21 DrawingFigures .40 O O 0.3 O 37 0 0 (46A 0 0 l 5 fl 0 102A A? 1270 54A I ma944? O l A O O .543 [22 322 69 G 122 O 0 100B 0 29 O 125 4&8 7 1023 til.525 5.34,

0 Q25 0 66B 0 O o o .54 o

PATENTEDAFR 1 1 I972 SHEET 3 [1F 7 PATENTEDAPR 11 1972 3,655,303

SHEET 5 [1F 7 I ENERGY ABSORBING ROTARY PISTON PUMP CROSS REFERENCE TORELATED APPLICATIONS This application is a continuation-in-part of U.S.application Ser. No. 756,035, filed Aug. 28, 1968 now U.S. Pat. No.3,549,110.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an energy absorbing device for aircraft arresting gear and aunique pump which is particularly useful therein.

2. Description of the Prior Art Various fluid-operated devices have beenused for absorbing energy in aircraft arresting gear. Most of suchenergy absorbing devices develop torque as a function of velocity whichenhances their energy-absorbing capacity. Their velocityresponsivenature, however, does not allow for sufficient torque control to obtainan efficient deceleration curve during the arrest, particularly for awide range of airplane weights and airplane engaging velocities.Hydraulic pumps having pressure related characteristics have beenproposed for such use, but no prexisting pump arrangements have hadsufficient capacity to absorb the peak energy required to arrest modernhigh speed aircraft. See British Pat. No. 287,189 (1928).

SUMMARY This invention utilizes several novel features which are usefulboth independently and in combination. An efiicient energy absorbingdevice is provided by mounting a rugged rotary pump having a pressurerelated characteristic within the interior of a substantially largecontainer of fluid. The fluid is circulated from the container throughthe pump and back into the container in response to rotation of thepump. This absorbs considerable mechanical input energy transmitted bythe pump to the substantial body of fluid in the container in the formof heat. Recirculation of the fluid within the container makes itpossible for a limited amount of fluid to absorb considerable energy.

A rotary piston pump is particularly effective for such service becauseof its simplicity and step down ratio between rotor and input shaftspeeds. This minimizes the mass of the pump necessary to provide a givenamount of energy absorption. Such a pump (which is also independentlyuseful) advantageously includes pressure relief-type or program actuatedoutlet valves and an inlet flow system including a hollow cam shafthaving radial port in the cam disc and triangular piston. Sealing meansof variable effectiveness may be provided between the triangular rotarypiston and the walls of the epitrochoidal housing within which itrotates to by-pass, minimize resistance of the pump at higher speeds ofoperation and to reduce the back pressure in the container required toprevent cavitation of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS Novel features and advantages of thepresent invention will become apparent to one skilled in the art from areading of the following description in conjunction with theaccompanying drawings wherein similar reference characters refer tosimilar parts and in which:

FIG. 1 is a perspective view of one embodiment of this invention beingused in an aircraft arresting gear;

FIG. 2 is a schematic diagram of the energy absorber shown in FIG. 1;

FIG. 3 is a bottom cross-sectional plan view taken through the energyabsorber shown in FIGS. 1 and 2 and through FIG. 4 along the line 3-3;

FIG. 4 is a cross-sectional view taken through FIG. 3 along the line4-4;

FIGS. SA-SE are schematic cross-sectional views taken through thehousing of the energy absorber shown in FIGS. 2-4 illustrating the cycleof operation of the inlet and outlet valves;

FIG. 6 is a perspective view of edge and side sealing means for therotary piston of the energy absorber shown in FIGS. 2-5;

FIGS. 7A and 7B are schematic diagrams showing operation of an optionalform of sealing means for bypassing fluid during high speed operation;

FIG. 8 is a front elevational view of another embodiment of thisinvention illustrating a rotary device and its fluid control system;

FIG. 9 is a side elevational view of the embodiment described in FIG. 8;

FIG. 10 is a front elevational view shown in FIGS. 23-9;

FIG. 11 is a cross-sectional view taken through the rotary device alonglines 11-11 of FIG. 10;

FIG. 12 is a schematic diagram illustrating the basic geometry of therotary device; and

FIGS. l3A-I3D are schematic diagrams illustrating various positions ofthe pistons and crankshaft of the rotary device during its operationalcycle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I is shown an airplane10 being arrested by aircraft arresting gear 12 engaging in hook 14extending from below the tail of aircraft 10. Aircraft arresting gear12, for example, includes a deck pendant or cable 16 extending acrossrunway 18 on flight deck 20 of naval aircraft carrier 22. Each end ofpendant 16 extends through sheave blocks 24A and B mounted on each sideof runway 18 and connected to long lengths of payout line, such as steelcable 26, which extend over pulleys 28A and B, 30A and B and throughdeck apertures 32 A and B to below-deck linear storage and payout device34. Device 34 is for example of the type utilizing steel cable asdescribed in copending application for U.S. Pat. Ser. No. 632,289 filedApr. 20, 1967, now U.S. Pat. No. 3,467,347, by this same inventor.Linear storage and payout device 34 may be of any effective type, suchas a simple reel of nylon tape, for example as described in U.S. Pat.No. 3,172,625. The cable or nylon (which may be referred to as a linearpayout element) and the storage device are mounted above and connectedto energy absorber 37 of system 36.

FIGS. 2-4 show energy absorbing system 36 including rotary piston-typepump 38 mounted within a container 40 of a substantial amount of fluid,such as ethylene glycol and water.

Rotary piston-type pump 38 is an adaptation of the rotary piston enginecommonly referred to as the Wankel engine. This engine is described invarious publications including: The Way the Things Work published bySimon and Schuster, New York, Second Printing, Library of CongressCatalog Card No. 67-2792; Paper 886d, presented Aug. 1964 at the S.A.E.National West Coast Meeting, entitled The Curtiss-Wright RotatingCombustion Engines Today by Charles Jones, Wright Aeronautical Division,Curtiss-Wright Corp.; an article in the Apr. 1966 issue of PopularScience Magazine, pages 98-107 entitled The Engine Thats Giving DetroitWankel Fever" by Devon Francis and U.S. Pat. No. 3,391,677.

Pump 38 as shown herein differs in many respects from the Wankel rotarypiston engine but similar terminology is employed herein for similarfeatures. Pump 38 may also be any rugged and dependable rotary pumphaving a pressure related characteristic, such as a gear or lobed pump.The rotary piston pump illustrated herein is particularly advantageousbecause of its relatively low mass relative to energy absorbingcapability by virtue of the slower rotation of its rotor relative toinput shaft speed for reasons later explained in detail.

Pump 38 includes triangular piston 42 rotating within housing 44 havingan epitrochoidal cross section, presenting an oval-shape slightlyconstricted in the middle. A pair of outlet valves 46A and B dischargefluid during discharge phases of operation into container or tub 40.Fluid is introduced to pump 38 through: axial inlet channel 48 andcutout sector 50 in rotary cam 49 and through radial ports 52 intriangular of the rotary device piston 42. The space between triangularpiston 42 and the inside of housing 44 is sealed by resilient wipers54A, B and C of the type described on page I06 of the aforementionedPopular Science article. Wipers 54A, B and C are generally referred toas wipers 54.

Pressure accumulator system 56 is provided for energizing the retrievalof cables 26A and B and for tensioning pendant 16 after retrieval.System 56 includes pressure storage cylinder 58 with free piston 69separating hydraulic fluid 62 from compressed air 64. The pressuresupply to cylinder 58 is provided through pipe lines 66A and B connectedto chamber 68A and 68B of pump housing 44. Lines 66A and 66B merge intoa single pipe line 70 connected to pressure cylinder 58 through checkvalve 72.

Retrieve motor 74 is supplied through pipe 76 connected to pressurecylinder 58 through control valve 78. Retrieve motor 74 is connected tolinear storage and payout device 34, for example through a sprocket andchain assembly 80. Since linear storage and payout system 34 might notbe capable of withstanding the force of pendant tensioning, tensioningcontrol device 82 is provided to bypass check valve 72. This permitspressure to be directed from cylinder 58 into pump chambers 68A and B inthe reverse direction, thus applying a very slight reverse displacementto pump 38, which is on the output or capstan side of the linear storageand payout system. This permits the linear payout elements and runwaypendant to be tensioned without unduly stressing the storage and payoutsystem. This is particularly important in the cable storage and payoutsystem described in the aforementioned copending patent application Ser.No. 632,289, filed Apr. 20, 1967, by this same inventor. Makeup fluidfor pressure cylinder 58 is stored in gravity tank 84 and adequatepressure in the system may be verified through pressure gauge 86.

In FIGS. 3 and 4 are shown details of energy absorbing device 37. FIG. 3is a plan view looking upwardly through a broken away portion of energyabsorber 37 when installed in the position shown in FIG. 1. FIG. 4 is across-sectional view taken through FIG. 3, illustrating energy absorber37 inverted from the position shown in FIG. I to facilitate illustrationof the working parts. FIG. 4 therefore shows shaft 88 pointingdownwardly instead of upwardly as it is actually installed in FIG. 1.

Energy absorber 37 in FIGS. 3 and 4 includes a pair of rotary pistons 42and 42X to eliminate the need for a counter weight. Piston 42 is lighterthan piston 42X by virtue of lightening holes 90 in piston 42 to providedynamic balance with respect to shaft 88. Rotary cam means 49 is alsomade lighter than rotary cam 49X by holes 92 in rotary cam 49 for thesame purpose. Bearing 125 of bronze material is disposed peripherallybetween cam 49, 49X and rotary piston 42 and 62X. Also the rotarypistons are laterally separated by a partition wall I27 thereby formingtwo separate chambers.

As shown in FIG. 3, output valves 46A and B are of the pressure relieftype and more particularly of the compressible fluid-actuated type,operated for example by compressed air trapped in chambers 94 withincylinders 96A and B. Valving assemblies 98A and B include pistons 100Aand B connected to valve discs 102A and B through stems 104A and B.Pistons 100A and B force valve discs 102A and B against 106A and B whenthe pressure in corresponding chambers is below a predetermined minimumpressure. The operating pressure may be varied by adjusting the pressureof compressed air in chambers 94A and B and this pressure may beprogrammed during portions of the cycle of operation if desired by apressure varying arrangement not shown.

The following description directed to piston 42 applies also to piston42X. Piston 42 is rotated in response to an input from shaft 88. Shaft83 includes threads 108 for attachment to a linear storage and payoutsystem. Enlarged portion H of shaft 88 is received within bearing H2,which is for example a journal bearing. Pressure for journal bearing H2is obtained from pump chambers 68A and B through space 114 betweenrotary piston 42X and adjacent plate H6 of container or cylinder 40.Pressure from bearing 112 is discharged through small holes 118extending into axial cavity 320 within shaft 88.

Inlet fluid 62 to pump 3% from container 40 is conducted through inletpassageway 48 and sector 50 within cam disc d9 whose sides 122 form anapproximate l20 angle. The base of cutout sector 50 is a portion of acircle 122 as shown in FIG. 3 to provide adequate flow through to innercam disc 49X. The cyclical phase of walls 122 of sector 50 relative toports 52A, B and C through piston 42 directs inlet fluid during properportions of the cycle into chambers 68A and B when they are not undercompression. In FIG. 2 chamber 68A is under compression, which liftsvalve disc 102A off its seat and discharges fluid through valve 46A.Valve fiB is closed because chamber 688 is not under compression andfluid is entering it through opened port 52A. Pressure is maintained bywiping seals 54, which are later described in detail in conjunction withFIGS. 6, 7A and 7B.

The phases of operation of rotary piston pump or energy absorber 37 areshown in FIGS. 5A through E, which illustrate the events occuring duringone rotation of input shaft 83 During this single rotation of shaft 88,cam disc 49 engaged within piston 42 makes one revolution and piston 42rotates in of a revolution. This rotation is effected by the describedcam action of disc 49 rotating within circular hole 125 in piston 42.Immersion of the piston 42 and cam 49 within fluid 62 adequatelylubricates relative rotation without undue wear and obviates the needfor gearing between the cam and piston. Such gearing might, however, beutilized in the same manner as it is utilized in combustion engineversions of the Wankel engine.

In FIG. 5A the blank portion of 49 is opposite port 52C. Chamber 68A istherefore sealed, thus causing rotation of piston 42 to compress thefluid therein and creating a pressure which moves valve 46A off its seatto discharge into container 40. At the same time sector 50 is connectedto port 52A which allows inlet fluid from container 40 to enter intochamber 683. Valve 46B is closed because there is not enough pressure toopen it. Outer seal 54A wipes in contact with the pinch 69 betweenchamber 68A and 688 in FIG. 5A.

In FIG. 5B piston 42 has rotated slightly clockwise, but substantiallythe same flow conditions exist, with valve 46A being open and valve 468being closed. There is one difference however, in that sector 50 is nolonger connected with valve port 52A but with valve port 528 to allowfluid to enter the lower portion of chamber 68A.

In FIG. 5C fluid is still entering chamber 68A through aligned sector 50and port 52B, but the pressure has as yet not been built up sufficientlyin chamber 688 to open discharge valve 463.

In FIG. 5D the pressure in chamber 63A has been built up sufficiently toopen discharge valve 468 and the arrows through it indicate thedirection of flow. Sector 50 is no longer communicating with valve port52B into chamber 68A, but with valve port 52C behind wiping seal 54A toallow fluid to flow into the portion of chamber 68B behind it.

In FIG. 5E valve 465 is still open between the seals effected by wipers54A and 5413 plus discharging pressure through valve 468 while fluid isentering chamber 688 behind seal 54A through sector 50 and connectingport 52C. One revolution of shaft 88 has therefore rotated triangularpiston 42 through via of a revolution. This provides a significantmechanical advantage and minimizes the mass of pump 38 to provide agiven amount of energy absorption. The energy ab sorbed is given up inthe form of heat into the body of fluid 62 within tub 40. Energyabsorber 37 is particularly effective with the illustrated rotarypiston-type of pump but an effective energy absorber may be provided byany rugged positive flow rotary pump such as a gear pump or a lobedpump.

FIG. 6 shows a form of wiping seal 54, including a spring urged wipingfeeler 12 within a radial slot 126 in a vertex of piston 42. An end sealis provided by resilient strip 128 in peripheral end slot 139. Theseseals are, for example, of the type described in the aforementionedliterature and patents relating to the Wankel type of internalcombustion engine.

FIGS. 7A and 7B show a modified form of seal 131 having variableeffectiveness in accordance with the internal pressure within housing38. Seals 131 include a spring bow 132 of relatively large area havingends 134 received within longitudinal slots 13-5 adjacent the verticesof piston 42. FIG. 7A illustrates a low pressure condition in which bowseal 132 firmly contacts against the wall of housing 44. This is thecondition that exists at relatively slow speeds of rotation and at norotation.

FIG. 78 illustrates how spring bow sealing element 132 is deflected backagainst the vertices of piston 42 under relatively high speed and highpressure conditions of flow to bypass fluid between the vertices ofpiston 42 and the wall of housing 38. This minimizes the size of theinlet port. For example, onehalf of the available flow from the pump isdissipated between the rotor tips and the housing. This reduces rotortip and housing wear and also reduces the stress level in the rotor.Spring bow wipers I32, for example, may be arranged to deflect andbypass at a pressure of 500 psi and over. Sealing to the housing isrequired to effect tensioning of the pendant 16 by means of a reversepressure flow back to the rotor as discussed in conjunction with FIG. 2and in the following detailed description of operation.

The power of an illustrative energy absorber of this type is, forexample, 62,500 horse power, which would be capable of arresting a125,000 airplane at 210 knots and 1,000 ft. ofline runout, withinrequired operational capabilities. This would give such an aircrfitarresting device an energy capacity of 24l,000,000 foot pounds with acable in a cable storage and payout system of the type described in theaforementioned copending application of 1% inches diameter. The cableweight, for instance, would be 3,600 pounds per engine making it 50percent of the lightest airplane to be arrested. The dynamic loads usedwith a nylon tape cable storage and payout system would also be minimal.Assuming a pressure in the pump of 3,000 psi, the maximum flow would be600 gallons per second or 26.5 gallons per shaft turn or 79.5 gallonsper turn ofthe rotor. FOr a 16 inch deep rotor the diameter of the rotorwould be 38 inches. With an allowable temperature rise of water at 40 F,the tub diameter would be approximately 8% feet storing 540 gallons. Itis believed that outlet valves 46 need not be programmed, but if suchbecomes necessary, it can be accomplished to adjust to airplane weightsranging from 1 1,000-125,000 pounds.

Another important advantage of this invention is that it provides anenergy absorber which is shallow enough to be mounted just under thedeck of an aircraft carrier. This isalso extremely important in view ofthe minimal space available aboard vessels.

During the arrest, the orifices in lines 66A and 66B permit pressure tobe accumulated in storage cylinder 58 for retrieval and pendanttensioning. Valves 46A and 46B are opened by pressure through lines 76,77, 79, 87A and 878 when retrieve valve 73 is opened. This minimizes thepressure necessary to operate retrieve motor 74. As shown in FIG. 2,orifices valve 85 allows main outlet valves 46A and 468 to close afterretrieve control valve 781s closed.

After retrieval, pendant i6 is tensioned by operating tensioning valve82. This operates rotor 42 in a direction opposite to its rotation whenabsorbing energy and exerts a pull on the capstan side (not shown) oflinear storage and payout system 34 when it is the type described in theaforementioned copending patent application and avoids the necessity oftransmitting tensioning loads through motor 7d, sprocket assembly 80 andthe connected portions of the linear storage and payout system 34. Onlya small displacement is needed to tension deck pendant 16, but somefluid will leak through the bearing. A makeup pump for the accumulator84 is therefore required to restore the necessary pressure and one-horsepower pump 138 is sufficient. During arrest, it is necessary to closethe tensioner valve 82 and this is accomplished from energy absorberpressure through lines 70 and 71 to tension valve 82. Tensioning mayalso be accomplished by a jacking motor (not shown) connected directlyto shaft 38 which eliminates t e need for the illustrated reversehydraulic and control cormections to pump 38.

FIGS. 8-11 show the pump control system 36A and details of rotary device38A, which is useful as a pump or energy absorber. The system 36Aconsists primarily of a circular container or reservoir 40A verticallymounted between two bearing blocks 91A and 91B. The reservoir 40Acontains hydraulic fluid 62A in which wall mounted rotary piston typepump 38A, is immersed. The rotary pump 38A includes a rotary cam orcrankshaft 49A engaged with triangular piston or rotor 42A that rotateswithin a housing 44A having an epitrochoidal cutout 45A. The cut-out 45Aforms two oval-shaped chambers 68A-68B. Connected to these chambers arediametrically opposing exhaust ports 47A and 478. From these opposingports are connected two exhaust piping circuits 53A and 53B that willlater be described in more detail. Crankshaft 49A has at its free end anaxial suction inlet port 48A that provides the necessary communicationbetween hydraulic fluid 62A via radial inlet ports 52A into chambers68A-68B. Crankshaft 49A includes drive shaft portion 88A that axiallyextends through the flanged end wall of reservoir 40A, seal 79 and asleeve bearing 81. Shaft 88A is connected to motor 89 through flexiblecoupling 93 to impart the necessary rotational power required by thepump.

For test purposes the reservoir 42A is rotatably mounted in bearings 91Aand 918. A bracket 77 extends parallel and radially downward from theside wall of reservoir 42 to which load cell 75 is attached, therebyallowing for the various required torque test. Counterweights 87A and87B are attached to crankshaft 49A to maintain the dynamic balancerequired, or unbalancing for test.

FIG. 12 illustrates the geometry details of the rotary pump 38A. Apinion gear 55 with center 57 is fixed to the stationary housing 44A.Rolling around this fixed pinion 55 is a ring gear 59 with center 61.This ring gear 61 is attached to the triangular piston or rotor 42Awhich has an outer point (R radially displaced from center 61. Whencenter 61 is rotated once around center 57 at a constant angularvelocity and with the gear teeth of pinion 55 and ring gear 59 in propermesh, a line from R to center 61 will rotate at ls this constant angularvelocity and point R will describe the element of the trochoid from R toR As center 61 is rotated two more times, point R will describe thetrochoid from R to R and from R back to the starting position R on thelast revolution of center 61. To accomplish this action with positivelyacting hardware, center 61 is driven by the crankpin (eccentric) of acrankshaft turning in the center 57 of the fixed pinion 55. Thus, therotor 42A makes one complete revolution for every three revolutions ofthe crankshaft 49A; and three points on the rotor 43A-43C, equidistantfrom center 61 and spaced apart, each generate the trochoidal housingcontour 45. The rotor 42A is machined to an appropriate arc betweenthese points so that a minimum positive clearance (c) exists at theposition shown in FIG. 13A.

The following schematic diagrams FIGS. TBA-13D illustrate variouspositions of piston 43A and crankshaft 49A, during operational cycle.

The rotary pump 30A is comprised of three pistons 43A-43C; that is eachof the three faces of the rotor 42A. The pistons, by moving with thecrankshaft 49A as we described previously, will suck fluid via axialinlet port 48A into the housing 44A and thence force it out of thehousing; through valved exhaust port 47A or 47B dependant upon pistoncycle position.

In FIG. 13A piston 43A is at top dead center. This means that thecrankshaft 49A has pushed the rotor face to a point of minimum volumebetween this face 43A and the housing 44A; i.e., minimum cylinder volumefor piston 43A. At this point it can be seen that the crankshaft inletport 48A has just opened to the mating port 52A in the rotor 42A (it hasin fact opened at 24.9 before T.D.C., measured in crankshaft rotation).The volume which will be swept by piston MA will fill from thecrankshaft l9A as shown in FIG. 13B, while fluid is being forced out ofthe machine by piston 413B, through the exhaust port 47B on theperiphery of the pump housing 44A.

Following the rotation of the crankpin center 61 about fixed center 57,as shovm in FIG. 13C that when the crankshaft 49A has turned 270piston43A has rotated 90 and is at bottom dead center (B.D.C.); i.e., maximumcylinder volume for the piston 43A. At this point the crankshaft inletport 48A just overlaps and closes the inlet port 52A for piston 43A, andthe discharge stroke commences.

Referring to FIG. 13B, piston 43C is at bottom dead center and FIG. 13Cshows piston 43C in its discharge stroke position.

In retracing the motion of the rotor as shown in FIGS. 13A and 13B, itwill be seen that piston 43A returns to top dead center in the next 270of crankshaft rotation. This condition is shown in FIG. 13D with piston43A facing the opposite exhaust port 47B from the condition shown inFIG. 13A, 540 earlier in the cycle.

Clearance between rotor tips R R and R and chamber wall 45A ranges from0.030 to 0.043 inches (average 0.037 inch) yet allows adequate operatingpressure to be maintained, such as maintaining 1,600 psi at 700 footpounds of shaft torque.

OPERATION F I68. 8 and 9 illustrate rotary piston type pump 38A, whichis a scale working model of a full size machine.

As shown in the drawings, hydraulic fluid 62A passes through axial inletchamber 33A into cut-out section 50A of rotor 42A, whereby it isdirected radially through ports 52A into chamber 68A. The slug of fluiddirected into chamber 68A is trapped by piston face 43A as rotor 42Arotates, whereby it is discharged into exhaust piping system 533 viaexhaust port 47B. Exhaust piping system 5313 is a pressure controllingsystem that conveys the fluid 62A from the exhaust port 478 to reservoirinlet 73B.

Fluid 62A leaves exhaust port 473, flows through tee 63B, havingconnected a pressure gauge 658, then through adjustable orifice 673 orfixed orifice plate 698. The fluid continues through shut-off valve 713,from which it reenters reservoir 40A at inlet 73B. Exhaust piping system53A connected between exhaust port 47A and 73A serves the identicalfunction. The adjustable and fixed orifices control the exhaust pressureand resultant torque in conjunction with the area of the clearancebetween the rotor tips and easing.

Iclaim:

1. A rotary piston pump comprising a housing having an epitrochoidalcross section with a pair of chambers, a triangular piston means withconvex sides and a centered circular aperture, rotary cam means havingcam disc means rotatably inserted within said circular aperture in saidpiston means for rotating it in said housing, said cam disc means beingsecured to a rotatable cam shaft means, outlet valve means in each ofsaid chambers, inlet conduit means extending radially through saidpiston means and through said rotary cam means whereby fluid isconducted into said chambers of said pump from which rotation of saidpiston means discharges it through said outlet valve means, inlet valvemeans disposed in said inlet conduit means, said inlet valve meanscomprising inlet valve port means extending radially through said pistonmeans, inlet channel means extending axially through said camshaft meansand radial cutout means through said cam disc means.

2. A rotary piston pump as set forth in claim 1 wherein said outletvalve means are of the pressure relief type.

3. A rotary piston pump as set forth in claim 1 wherein said housingincludes a dividing pinch between said chambers, and said outlet valvemeans comprise a pair of outlet valves each disposed adjacentdiametrically opposite sides of said pinch for prolonging thecompression portion of the pumping cycle.

4. A rotary piston pump as set forth in claim 1 wherein said radialcutout means in said cam disc means approximately comprises a sector insaid cam disc means.

5. A rotary piston pump as set forth in claim 5, wherein said sectorcovers arpproximatelv and the corresponding portrons of said in e valveport means through said piston means cover substantially less are thanthe contacting portions of said sectors.

1. A rotary piston pump comprising a housing having an epitrochoidalcross section with a pair of chambers, a triangular piston means withconvex sides and a centered circular aperture, rotary cam means havingcam disc means rotatably inserted within said circular aperture in saidpiston means for rotating it in said housing, said cam disc means beingsecured to a rotatable cam shaft means, outlet valve means in each ofsaid chambers, inlet conduit means extending radially through saidpiston means and through said rotary cam means whereby fluid isconducted into said chambers of said pump from which rotation of saidpiston means discharges it through said outlet valve means, inlet valvemeans disposed in said inlet conduit means, said inlet valve meanscomprising inlet valve port means extending radially through said pistonmeans, inlet channel means extending axially through said camshaft meansand radial cutout means through said cam disc means.
 2. A rotary pistonpump as set forth in claim 1 wherein said outlet valve means are of thepressure relief type.
 3. A rotary piston pump as set forth in claim 1wherein said housing includes a dividing pinch between said chambers,and said outlet valve means comprise a pair of outlet valves eachdisposed adjacent diametrically opposite sides of said pinch forprolonging the compression portion of the pumping cycle.
 4. A rotarypiston pump as set forth in claim 1 wherein said radial cutout means insaid cam disc means approximately comprises a sector in said cam discmeans.
 5. A rotary piston pump as set forth in claim 5, wherein saidsector covers approximately 120* and the corresponding portions of saidinlet valve port means through said piston means cover substantiallyless arc than the contacting portions of said sectors.